The present invention relates to the preparation and utilization of monolayer particulate films and, more specifically, to the utilization of monolayer films in applications such as semiconductor fabrication, photoresist processing, dielectric layering, integrated optical device fabrication, polymer science, adhesive technology, etc.
Particulate films that are on the order of one molecule or one particle thick are commonly referred to as ultrathin films, monomolecular layers, or monolayer films. Monolayer films are commonly produced from amphiphilic low molecular weight molecules, i.e., molecules that include a polar end and a non-polar or hydrophobic end. Disposed on the surface of a non-solvent, such as water, the polar ends of the molecules or particles will tend towards the water, while the nonpolar or hydrophobic ends will tend to project into the gas space above. Typically, small amounts of such amphiphilic substances are dissolved in a suitable solvent and, for example, introduced onto a water surface of sufficient size. The solution spreads across the surface of the water and, with evaporation of the solvent, the molecules form an initially noncohesive, monomolecular layer. By moving a suitable barrier, the water surface is reduced in size in a dimension along the surface of the water and the non-cohesive layer is compressed into a cohesive, monomolecular layer exhibiting order at the molecular level. When this quasi-solid state of this monomolecular layer is reached, further movement of this barrier meets with a clearly measurable resistance, which indicates that the cohesive state has been reached. Suitable substrates can then be immersed through the monomolecular layer into the water and in turn become coated with a cohesive monomolecular layer of the amphiphilic substance. The stated process can be repeated. This coating technique is known to those skilled in the art as the Langmuir-Blodgett technique.
Ultra-thin films prepared and applied using conventional Langmuir-Blodgett techniques are not however completely free from voids between the molecules or particles of the film. As a result, the ultra-thin films prepared according to the conventional Langmuir-Blodgett techniques may be unsuitable for specific thin film applications, particularly those related to the fabrication of semiconductor devices. Accordingly, the present inventor has recognized a need for an improved technique for preparing and utilizing cohesive monolayer films.
This need is met by the present invention wherein an improved process and apparatus for processing a monolayer film and transferring the monolayer film to a substrate are provided. For the purposes of defining and describing the present invention, it is noted that a monolayer film may comprise a monolayer particulate film or a monomolecular film.
In accordance with one embodiment of the present invention, a process for transferring a monolayer film to a substrate is provided comprising the steps of: (i) providing a film of process particles and a process particle carrier media such that the film of process particles is disposed proximate an upper surface of the carrier media, and such that the film of process particles incorporates voids between the process particles; (ii) sonicating the carrier media to form micro-bubbles in the carrier media, wherein the sonication contributes to a decreased degree of void incorporation in the film of process particles; and (iii) transferring the film of process particles to a surface of the substrate. The film of process particles is preferably disposed along the upper surface of the carrier media. The step of sonicating the carrier media may additionally result in formation of the micro-bubbles at the upper surface of the carrier media. The film of process particles preferably comprises a monolayer film.
In accordance with another embodiment of the present invention, a method of processing a monolayer film is provided comprising the steps of: (i) providing a film of process particles and a process particle carrier media such that the film of process particles is disposed proximate an upper surface of the carrier media, and such that the film of process particles incorporates voids between the process particles; and (ii) sonicating the carrier media to form micro-bubbles in the carrier media, wherein the sonication contributes to a decreased degree of void incorporation in the film of process particles.
In accordance with yet another embodiment of the present invention, a process for transferring a monolayer film to a substrate is provided comprising the steps of: (i) providing a water-based carrier media defining an upper surface; (ii) introducing process particles on the upper surface of the carrier media, wherein the particles are dissolved in a solvent and the particles and the solvent are insoluble in the carrier media; (iii) evaporating the solvent such that a non-cohesive monolayer film of the particles is formed on the upper surface of the carrier media; (iv) decreasing a degree of void incorporation in the monolayer film of particles by compressing a dimension of the non-cohesive film along the upper surface of the carrier media, and sonicating the carrier media to form micro-bubbles in the carrier media, wherein the compression and the sonication contribute to a decreased degree of void incorporation in the film of process particles; and (v) transferring the film of particles to a surface of the substrate. The steps of compressing and sonicating may be executed concurrently.
In accordance with yet another embodiment of the present invention, a method of processing a monolayer film is provided comprising the steps of: (i) providing a water-based carrier media defining an upper surface; (ii) introducing process particles on the upper surface of the carrier media, wherein the particles are dissolved in a solvent and the particles and the solvent are insoluble in the carrier media; (iii) evaporating the solvent such that a non-cohesive monolayer film of the particles is formed on the upper surface of the carrier media; and (iv) decreasing a degree of void incorporation in the monolayer film of particles by compressing the non-cohesive film, and sonicating the carrier media to form micro-bubbles in the carrier media, wherein the compression and the sonication contribute to a decreased degree of void incorporation in the film of process particles.
In accordance with yet another embodiment of the present invention, a process for transferring a monolayer film to a substrate is provided comprising the steps of: (i) providing a water-based carrier media defining an upper surface; (ii) introducing process particle molecules on the upper surface of the carrier media, wherein the molecules include a polar end and a hydrophobic end, the molecules are dissolved in a solvent, and the molecules and the solvent are insoluble in the carrier media; (iii) evaporating the solvent such that a non-cohesive monolayer film of the molecules is formed on the upper surface of the carrier media; (iv) decreasing a degree of void incorporation in the monolayer film of molecules by compressing a dimension of the non-cohesive film along the upper surface of the carrier media to yield a predetermined compressed film surface tension, and by sonicating the carrier media over a predetermined sweep frequency through a sonication energy transfer bath sonically coupled to the carrier media to form micro-bubbles in the carrier media, wherein the compression and the sonication contribute to a decreased degree of void incorporation in the film of process particles; and (v) transferring the film of molecules to a surface of the substrate by drawing the substrate through the carrier media and the film of process particles, and maintaining the sonication and the compressed film surface tension as the substrate is drawn through the carrier media and the film of process particles.
In accordance with yet another embodiment of the present invention, an apparatus for transferring a monolayer film to a substrate is provided comprising a carrier bath, a compression member, at least one sonication transducer, a substrate draw, and a film surface tension controller. The carrier bath is arranged to contain a process particle carrier media such that the carrier media defines an upper surface. The compression member is arranged to compress a film of process particles disposed proximate the upper surface of the carrier media. The compression increases the film surface tension of the film of process particles. The sonication transducer is arranged to sonicate the carrier media to form micro-bubbles in the carrier media. The compression member and the sonication transducers are arranged to decrease collectively a degree of void incorporation in the film of process particles. The substrate draw is arranged to pass the substrate through the film of process particles and the film surface tension controller is arranged to maintain the film surface tension. The film surface tension controller may be arranged to maintain the film surface tension as the substrate is passed through the film of process particles and as the carrier media is sonicated.
In accordance with yet another embodiment of the present invention, an apparatus for preparing a monolayer film is provided comprising a carrier bath, a compression member, at least one sonication transducer, and a film surface tension controller. The carrier bath is arranged to contain a process particle carrier media such that the carrier media defines an upper surface. The compression member is arranged to compress a film of process particles disposed proximate the upper surface of the carrier media. The compression increases the surface tension of the film of process particles. The sonication transducer is arranged to sonicate the carrier media to form micro-bubbles in the carrier media. The compression member and the sonication transducers are arranged to decrease collectively a degree of void incorporation in the film of process particles. The film surface tension controller arranged to maintain the film surface tension.
In accordance with yet another embodiment of the present invention, an apparatus for transferring a monolayer film to a substrate is provided comprising a carrier bath, a transfer bath, a draw bath, a compression member, a film surface tension monitor, an array of sonication transducers, a substrate draw, and a film surface tension controller. The carrier bath is arranged to contain a process particle carrier media such that the carrier media defines an upper surface. The carrier media is selected such that the process particles are insoluble in the carrier med. The transfer bath is sonically coupled to the carrier bath and is arranged to contain a sonic energy transfer fluid therein. The draw bath is arranged to accommodate the substrate therein in an orientation substantially perpendicular to the upper surface of the carrier media. The compression member is arranged to compress a film of process particle molecules disposed proximate the upper surface of the carrier media, wherein the compression increases the surface tension of the film. A film surface tension monitor is arranged to measure the film surface tension. The array of sonication transducers are arranged to sonicate the carrier media over a predetermined sweep frequency through the transfer bath to form micro-bubbles in the carrier media. The compression member and the sonication transducers are arranged to decrease collectively a degree of void incorporation in the film of process particles. The substrate draw is arranged to transfer the film of process particle molecules to a surface of the substrate by drawing substrate from the draw bath through the carrier media and the film of process particles. The film surface tension controller arranged to maintain the film surface tension as the substrate is passed through the carrier media and the film of process particles.
Accordingly, it is an object of the present invention to provide an improved technique for preparing and utilizing cohesive monolayer films. Other objects of the present invention will be apparent in light of the description of the invention embodied herein.